Mineral fiber products are commonly produced by melting the base mineral material and then fiberizing the molten liquid. The primary fibers so produced are attenuated into smaller diameter fibers of finite length which typically are deposited onto a moving support or collection surface to form a mass or layer of uniformly distributed intertwined fibers. Liquid binder sprayed on the fibers as they move toward the support is subsequently set or cured in an oven through which the layer of fibers passes. The layer is often compressed to a predetermined density prior to the setting of the binder.
Because many of the properties of fibrous products produced in this manner are limited by the properties of the base fibers themselves, it would at times be beneficial to modify the products in order to alter or enhance those properties, to add strength to the products, to reduce costs or to modify density or other properties. A major problem encountered in introducing additive materials, however, is the difficulty in uniformly distributing them throughout the fibrous matrix. If liquid additives are not sticky, they may be difficult to adhere to the fibers when sprayed onto the fibers as they move toward the collection surface. If liquid additives are sprayed onto an already formed fibrous mass, it is difficult to uniformly disperse them throughout the mass. It is even more difficult to add solid additives to a layer or mass of collected fibers so as to uniformly penetrate and become dispersed throughout the mass. If the particular additive desired to be added is available only in solid form, the present state of the art of introducing it to the fibrous product dictates against such addition.
It would therefore be highly desirable to be able to introduce solid particles to a fibrous product in such a way that the particles are uniformly distributed throughout the product. Further, the method of introduction should be such that it does not adversely affect the production of the base fibers or interfere with the normal collection and depositing of the produced fibers. In addition, the cost of introducing additives should be minor so as not to be a deterrent to the additive project.